public class MyLinkedList implements IList{

    static class ListNode{
        public int val;
        public ListNode prev;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }

    public ListNode head;
    public ListNode last;

    @Override
    public void addFirst(int data) {
        ListNode node=new ListNode(data);
        if (head==null){
            head=last=node;
        }else {
            node.next=head;
            head.prev=node;
            head=node;
        }

    }

    @Override
    public void addLast(int data) {

        ListNode node=new ListNode(data);
        if (head==null){
            head=last=node;
        }else {
            node.prev=last;
            last.next=node;
            last=node;
        }
    }

    @Override
    public void addIndex(int index, int data) {
        int len=size();
        if (index<0 || index>len){
            return;
        }
        if(index==0){
            addFirst(data);
            return;
        }
        if (index==len){
            addLast(data);
            return;
        }
        ListNode node=new ListNode(data);
        ListNode cur=findIndex(index);
        node.next=cur;
        cur.prev.next=node;
        node.prev=cur.prev;
        cur.prev=node;


    }

    private ListNode findIndex(int index){
        ListNode cur=head;
        while (index!=0){
            cur=cur.next;
            index--;
        }
        return cur;
    }

    @Override
    public void remove(int key) {
        ListNode cur=head;
        while(cur!=null){
            if (cur.val==key){
                if (cur==head){
                    head=head.next;
                    if (head!=null){ //是否只有一个节点
                        head.prev=null;
                    }
                }else {
                    cur.prev.next=cur.next;
                    if (cur.next==null){
                        last=last.prev;
                    }else {
                        cur.next.prev=cur.prev;
                    }
                }
                return;
            }
            cur=cur.next;

        }
    }

    @Override
    public void removeAllKey(int key) {
        ListNode cur=head;
        while(cur!=null){
            if (cur.val==key){
                if (cur==head){
                    head=head.next;
                    if (head!=null){ //是否只有一个节点
                        head.prev=null;
                    }
                }else {
                    cur.prev.next=cur.next;
                    if (cur.next==null){
                        last=last.prev;
                    }else {
                        cur.next.prev=cur.prev;
                    }
                }
            }
                cur=cur.next;
        }
    }



    @Override
    public void clear() {
        ListNode cur=head;
        while (cur!=null){
            ListNode curN=cur.next;
            cur.next=null;
            cur.prev=null;
            cur=curN;
        }
        head=last=null;
    }

    @Override
    public boolean contains(int key) {
        ListNode cur=head;
        while (cur!=null){
            if (cur.val==key){
                return true;
            }
            cur=cur.next;
        }
        return false;
    }
    @Override
    public int size() {
        ListNode cur=head;
        int num=0;
        while (cur!=null){
            num++;
            cur=cur.next;
        }
        return num;
    }

    @Override
    public void display() {
        ListNode cur=head;
        while (cur!=null){
            System.out.print(cur.val+" ");
            cur=cur.next;
        }
        System.out.println();
    }
}



